Birefringence in the Cholesteric Unwinding Region

Birefringent areas exhibit a wide spectrum of higher order colors in the unwinding region separating the true cholesteric from the high density phase. The image presented above illustrates the colors and textures observed in this region. The DNA concentration in this experiment is approximately 250 milligrams per milliliter, and the photomicrograph magnification is approximately 400x. Originally recorded on Fujichrome 64T transparency film using a Nikon Optiphot-Pol microscope with crossed polarized illumination, the image was digitized using a Nikon CoolScan transparency film scanner. Exposures were recorded about 3 f-steps under the recommended value given by an in-camera photomultiplier and were push-processed approximately 1.75 f-steps in the first E-6 developer.